This invention relates generally to crop harvesting and threshing machine, more commonly known as combines, and more particularly to the infeed area that is immediately adjacent to the forward portion of the threshing and separating rotor. This infeed area is utilized to impart a radial direction of crop material flow to the crop material as it enters the threshing and separating chamber which contains the threshing and separating rotor. Specifically, the invention is concerned with the geometry of this infeed area to maximize the amount of crop material which can be passed through the combine during field operation. This invention is equally applicable to an axial flow type of combine utilizing either a single threshing and separating rotor or multiple threshing and separating rotors.
Conventional type of combines pass the crop material to be threshed between a rotary cylinder and a stationary concave in a direction that is normal to the axis of the rotating cylinder and parallel with the longitudinal axis of the frame. In this system much of the grain contained in the crop material fed to the cylinder and the concave passes through the concave as grain. The remainder of the material is conveyed to separating elements of the combine that traditionally include reciprocating or oscillating straw walkers, return pans, and chaffer sieves. Such conventional combines suffer from the major disadvantage of having a threshing capacity that is limited by the single pass of the crop material about the threshing cylinder.
Combines of the axial flow type, in contrast, utilize single or dual threshing and separating rotors that permit the crop material to spiral rearwardly about each rotor thereby passing over the concave during the threshing process three or more times. This increased exposure to the rotor of the crop material as it spirals thereabout during the threshing process permits axial flow type of combines to increase the amount of grain obtained from any crop passed therethrough when compared with conventional combines.
The current axial flow combines utilize various means at the entrance point of the rotors to induce primarily an axial motion to the crop material until it enters the concave area. At this point, the crop material is accelerated into a radial path around the rotors. It is this radial path with its centrifugal force that accomplishes centrifugal threshing of the crop material. The key to efficient threshing and separating in axial flow combines is the early imparting of this radial motion to the crop material so that the spiralling action is initiated as soon as possible during the threshing process.
Different infeed geometries have been experimented with in each of the various type of axial flow combines in attempts to enhance the throughput characteristics of these relatively recent commercial machines. Additionally, roping of crop material, where the crop material forms rope-like tangled masses, especially common in tough green crop conditions, occasionally has been a problem in some designs.
The foregoing problems are solved in the design of the machine comprising the present invention by providing a crop thinning chamber or infeed area to the threshing and separating rotor having an improved geometry which facilitates imparting early in its travel a radial motion to the crop material as it enters the threshing and separating cylinders.